VIPA CP 240 RS232, Manual

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Manual VIPA System 200V Chapter 5 CP 240 - EnOcean
HB97E - CP - Rev. 11/30 5-7
Communication principle
The CPU writes data via the back plane bus, which is to be sent, into the
according data channel. The communication processor enters them into a
ring buffer (2048Byte) and transmits them then via EnOcean.
When the communication processor receives data via EnOcean, the data
is stored in a ring buffer (2048Byte). The received data may now be read
telegram by telegram (11Byte) from the CPU via the data channel .
The exchange of received telegrams via back plane bus happens
asynchronously. When a complete telegram has been arrived via
EnOcean, it is stored in the buffer. The length of the ring buffer limits the
maximum number of telegrams. At full buffer new telegrams are ignored.
Out of the telegrams of 14Byte length telegram by telegram 11Byte user
data are transferred to the CPU via back plane bus. The first two sync
bytes and the Checksum are not handled over.
A telegram that is to send has to be transferred to the CP 240. This
supplements the telegram with the first two sync bytes and the Checksum
and handles the telegram on to the send buffer. The CP 240 compiles
these blocks in the send buffer and sends it via the EnOcean transceiver
as soon as the telegram is complete. Since the data transfer via back plane
bus happens asynchronously, a "software handshake" is used between
CP 240 and CPU. The registers for the data transfer from the CP 240 have
a width of 16Byte. For the handshake, the Bytes 0 to 3 (word 0 and 2) are
reserved.
The following picture shall illustrate this:
V-Bus
SEND
OUT
IN
Byte 14
. . .
Bte4
Byte 2/3
Byte 0/1
Byte 14
. . .
Byte 2/3
Byte 0/1
Byte 4
Byte 4
Soft handshake via Byte 0 ... 3
TxD Cnt
RxD Cnt
TxD Cnt
RxD Cnt
Communications processor
REC
SEND
2048Byte
2048Byte
REC
11Byte
11Byte 14Byte
14Byte
EnOcean
14Byte
14Byte
MC
Send and receive
data
Communication
via back plane bus
Tasks of the CPU